Laminated finger seal with stress reduction

ABSTRACT

A finger seal for use between a housing and a combustor liner to inhibit air passage therebetween. The finger seal has at least two annular diaphragm members partitioned into a generally continuous inner diameter portion and a segmented outer diameter portion. The segments are finger elements spaced uniformly apart forming gaps therebetween and extend radially outward terminating in a foot portion. A keyhole is formed at the terminus end of the gaps to reduce fatigue and stress of the finger elements. The diaphragm members are laminated together, oriented such that adjacent fingers of one laminate block the gaps of the other, and inserted between a pair of spacers and endplates to be attached at their inner diameter portion. The finger seal is attached circumferentially around the housing and assembled into the combustor liner with the foot portion sealing against the combustor liner interior wall.

GOVERNMENT RIGHTS

[0001] The United States Government has rights in the present invention pursuant to Contract No. F-3361598-C-2803 issued by the U.S. Air Force and DMH-1098-C-0023 issued by the U.S. Army.

BACKGROUND OF THE INVENTION

[0002] This invention relates to sealing devices disposed relative to two generally stationary structures of approximately cylindrical shape and to providing an air seal therebetween. The present invention provides air sealing of combustor liners that typically have large temperature excursions and experience deflection relative to the adjacent structures.

[0003] The present art uses a series of interlocking ceramic segments disposed around a combustor liner for sealing. The ceramic segments are biased against the combustor by metallic springs. This seal structure provides air-to-air sealing between the two elements while allowing relative motion between the bodies. Such seals, which spring loading feature is used in other sealing applications as disclosed in U.S. Pat. No. 4,415,317, intended for other structures, are expensive to manufacture, subject to premature failure of individual spring elements and are complex to install in the application.

[0004] Laminated finger seals are know in the art as exemplified by U.S. Pat. No. 5,108,116. These seals are designed for fluid sealing between relatively rotating elements as for example a shaft and a housing. As a result of this application, the fingers, which may have a foot element, are designed to slide on the shaft element when rotating. The finger portion provides pressure through the foot portion to maintain contact with the rotating shaft. A balance must be maintained to avoid excessive wear of the foot portion and the rotating shaft. There exist various improvements in designs for the foot portion, as for example to give it aerodynamic properties to glide over the surface of the shaft. In such an application a considerable amount of pressure can be exerted by the finger elements to maintain a tight seal interface and aerodynamic or sliding motion at low friction levels is not required.

[0005] For the combustion liner type interface sealing application, the combustor liner in operation is at an elevated temperature relative to the surrounding structure. A finger seal inserted therebetween may have the finger elements extended radially outward for engagement with the combustor liner. The inner circumference of the seal may then be attached to the housing.

[0006] While attaching sealing elements to the rotating part of a system to project sealing elements radially outward are known, as for example German Patent No. 626,541, these devices have not used the finger seal technology of the present invention. Again, as discussed about, the seals are intended for relative rotating elements and must compromise sealing efficiency with wear of components such as combs or brushes. Although such seals include a radially outward projection of seal combs or brushes they are not radially compliant making them unsuitable for the air seal environment of the present invention.

[0007] A type of seal having shallow grooves for lubrication is disclosed in U.S. Pat. No. 3,744,805. While the grooves extend radial outward from a solid inner circumferential surface, the grooves are not gaps between radial extending fingers as in the present invention. The type of seal disclosed is designed for axial motion rather than for radial deflection as in the present invention.

[0008] As can be seen, there is a need for a generally circular sealing device for fluid sealing between two bodies experiencing relative radial motion and elevated temperatures.

SUMMARY OF THE INVENTION

[0009] In one aspect of the present invention, a laminated finger seal may be inserted between two generally stationary structures to inhibit airflow therebetween. The seal has multiple diaphragm members laminated together and fixed in a holding device. The diaphragm members are circumferential bands having a generally continuous inside diameter portion and a segmented outside diameter portion.

[0010] The segmented portion defines a circumferentially uniform array of finger elements spaced apart to define a plurality of uniform gaps. When the seal is clamped in the holding device attached to the housing and assembled into the combustor liner the finger elements are deflected toward the inner circumference of the finger seal thereby applying pressure against the combustor liner wall to affect the sealing between the structures.

[0011] In another aspect of the present invention, the uniform gaps of the diaphragm members have a stress reducing keyhole formed at the terminal end thereof. The diaphragm members are laminated together and disposed between a pair of spacers and the combination clamped between a pair of endplates.

[0012] In a further aspect of the present invention, the finger elements have a foot portion at an outermost end for sealing engagement with a combustor liner.

[0013] These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 illustrates a partial perspective view of a combustor liner with finger seal installed;

[0015]FIG. 2 illustrates a partial side view of a diaphragm member of the present invention;

[0016]FIG. 3 illustrates a cross-sectional view of an assembled finger seal of the present invention;

[0017]FIG. 4 illustrates a partial view of a housing and combustor liner with finger seal contained therebetween.

DETAILED DESCRIPTION OF THE INVENTION

[0018] The following detailed description is of the best currently contemplated modes of carrying out the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims.

[0019] Referring to FIG. 1, a seal 20 may be mounted against a combustor liner 14 adjacent an exit nozzle 12 of a combustor (not shown). The finger seal 20 may be disposed circumferentially about and attached to the housing 10. The outer circumference 22 of the seal 20 may then engage the wall of combustor liner 14. The seal 20 serves to inhibit leakage of air into the combustion chamber.

[0020] Referring to FIGS. 1 through 4, the seal 20 may be comprised of a plurality of diaphragm members 30 or thin annular metallic bands laminated together and retained between spacers 50. The diaphragm members 30 have a generally continuous inner diameter portion 32 and a segmented outer diameter portion 34 having relatively flexible finger elements 36 extending radially outward from an inner relatively rigid portion. The spacers 50, resembling washers, when clamped with the diaphragm members 30 between endplates 60 prevent the segmented outer diameter portion 34 from being axially pinched by directing the clamping load through the radially inner diameter portion 32. End plates 60 provide structure for engagement with a holding device such as a clamp. Depending on the particular application the end plates 60 may not be necessary. The use of the finger seal type configuration in a non-rotational sealing application allows for a tight air seal with flexibility for radial motion of a housing and combustor liner as compared to prior art use of blades or wire sealing methods. In addition, the stress relief keyhole located at the terminal end of the gaps 42 formed between the flexible finger elements 36 increases the useful life of the seal 20.

[0021] Referring to FIG. 2, the outer diameter portion 34 may be comprised of finger elements 36 extending radially outward from the inner diameter portion 32 and having a foot portion 38 at their radially outermost end 40 cooperatively defining an outer diameter. The form of the finger elements is generally a comb-like structure as with other finger seal devices known to those skilled in the art. The finger elements 36 may be spaced apart by gaps 42 in a uniform manner with the finger elements 36 and inner diameter portion having about the same thickness. The orientation of the finger elements 36 is new relative to previous known finger seals in that the finger elements 36 extend radially outward and the foot portion 38 outer circumferential 22 surface requires no provision for contact with a rotating surface.

[0022] In addition the diaphragm member 30 has a keyhole 44 formed at the terminus end 46 of gaps 42 for stress relief of the finger elements 36 by increasing the relative small diameter terminal end of gaps 42 allowing additional dispersion of stress force to the inner diameter portion 32 and to increase low cycle fatigue life as a result of the increased dispersion of stress forces. The finger and gap structure of the seal 20 facilitate sealing contact with a surface such as that of liner 14. When inserting the housing 10 and attached seal 20, a slight rotation of the seal in a counter clockwise direction as viewed in FIG. 2 allows firm seating of the outer circumference foot portion 38. The foot portion 38 outer face is pressed against the combustor liner 14 inner wall as the finger elements 36 are deflected radially inward. The rotation of the seal 20 in a counter clockwise direction utilizes the generally clockwise orientation of the finger elements 36, as best viewed in FIG. 2, to facilitate deflection and seating of the finger elements 36.

[0023] In use, there generally is no relative motion between the housing 10 and liner 14 in a rotational direction, the seal 20 may be seated such that the finger elements 36 engage the liner 14 using the desired pressure or force to achieve the required air-to-air sealing between structures. The pressure of the finger elements 36 may not be limited by the need to allow for rotational motion between the housing 10 and combustor liner 14. Therefore, within the deflection stress limits of the material structure of the finger elements 36 and the desired relative deflection extremes between the housing 10 and combustor liner 14, the seal 20 may be seated between the bodies to minimize air leakage.

[0024] There normally may be relative radial an axial motion between the housing 10 and liner 14 due to temperature differential caused expansion and contraction as well as structure vibration motion. Such movement may be accommodated by the finger elements 36 of the seal 20. A diaphragm member 30 constructed of metal as discussed above provides suitable air flow sealing in this application. As can be appreciated, the flexibility of the finger elements 36 allows deflection between the structures by compression and extension of finger elements in the direction of an applied force such as a vibration.

[0025] Referring to FIGS. 3 and 4 the seal may be an assembly of a plurality of diaphragm members 30, spacers 50 and endplates 60. The diaphragm members 30 may be laminated together in quantities of 2 or more depending on the sealing requirements. The laminates may be fastened along the inner diameter portion 32 of the diaphragm members 30 thereby allowing freedom of motion of the finger elements 36. This fastening may be by riveting 62, soldering, welding or other fastening means. The diaphragm members 30 are assembled side by side with adjacent laminates offset or positioned such that the fingers of one block the gaps of the other. The diaphragm members 30 have pairs of apertures 48 to allow offset of adjacent members.

[0026] The laminated diaphragm members 30 may be disposed between spacers 50 and a pair of endplates 60 for attachment to the housing 10. FIG. 3 illustrates a configuration in which rivets 62 are used to fasten the seal 20 assembly. The seal 20 may then be attached circumferentially around the housing 10 with a clamping mechanism 64. Thus the inner diameter portion 32 of each diaphragm member 32 may be fixedly restrained and the outer diameter portion 34 rests in flexible contact with the liner 14.

[0027] It should be understood, of course, that the foregoing relates to preferred embodiments of the invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims. 

We claim:
 1. A seal for air sealing of a combustor liner comprising: a plurality of annular diaphragm members having an inner diameter portion and an outer diameter portion wherein said inner diameter portion is generally continuous and said outer diameter portion is segmented; said outer diameter portion having a plurality of radially extending finger elements defining an outer circumference and generally uniformly spaced apart having a gap formed therebetween; said diaphragm members laminated together and fastened along said inner diameter portion wherein adjacent diaphragm members are oriented such that said finger elements of one diaphragm member block said gaps of a second diaphragm member; and said diaphragm members disposed between a pair of spacers fixidly attached for engagement with a means for attachment to a housing.
 2. The seal as in claim 1 wherein said outer diameter portion having at a terminus end of said gaps a keyhole formed therein to reduce stress caused by flexure of said finger elements.
 3. The seal as in claim 1 wherein said finger elements having a foot portion at an outermost end for sealing engagement with a combustor liner.
 4. The seal as in claim 1 wherein said diaphragm members and said spacers are fixedly attached between a pair of end plates for engagement with the means for attachment to a housing.
 5. The seal as in claim 4 wherein said diaphragm members, said spacers and said end plates are clamped to the housing for positioning of the seal adjacent a combustor exit nozzle and said finger elements engage a combustor liner.
 6. A seal for air sealing between a housing and a combustor liner comprising: a plurality of annular diaphragm members having an inner diameter portion and an outer diameter portion wherein said inner diameter portion is generally continuous and said outer diameter portion is segmented; said outer diameter portion having a plurality of radially extending finger elements defining an outer circumference and generally uniformly spaced apart having a gap formed therebetween wherein said outer diameter portion having at a terminus end of said gaps a keyhole formed therein; said diaphragm members laminated together and fastened along said inner diameter portion wherein adjacent diaphragm members are oriented such that said finger elements of one diaphragm member block said gaps of a second diaphragm member; and said diaphragm members disposed between a pair of spacers and the combination fixidly attached between a pair of end plates for engagement with a means for attachment to a housing.
 7. The seal as in claim 6 wherein said finger elements having a foot portion at an outermost end for sealing engagement with a combustor liner.
 8. The seal as in claim 6 wherein said diaphragm members, said spacers and said end plates are clamped to the housing for positioning of the seal adjacent a combustor exit nozzle and said finger elements engage a combustor liner.
 9. A seal for air sealing between a housing and a combustor liner comprising: a plurality of annular diaphragm members having an inner diameter portion and an outer diameter portion wherein said inner diameter portion is generally continuous and said outer diameter portion is segmented; said outer diameter portion having a plurality of radially extending finger elements defining an outer circumference, wherein said finger elements having a foot portion at an outermost end for sealing engagement with a combustor liner, and generally uniformly spaced apart having a gap formed therebetween wherein said outer diameter portion having at a terminus end of said gaps a keyhole formed therein; said diaphragm members laminated together and fastened along said inner diameter portion wherein adjacent diaphragm members are oriented such that said finger elements of one diaphragm member block said gaps of a second diaphragm member; and said diaphragm members disposed between a pair of spacers and the combination fixidly attached between a pair of end plates for engagement with a means for attachment to a housing.
 10. A method for air sealing between a housing and a combustor liner, the steps comprising: laminating a plurality of annular diaphragm members having a generally continuous inner diameter portion and a segmented outer diameter portion; orienting the diaphragm members such that the segmented outer diameter portion comprising a plurality of radial outward extending finger elements having a gap formed therebetween have the finger elements of one diaphragm member covering the gaps of an adjacent diaphragm member; assembling the diaphragm members between a pair of spacers and attaching the assembly between a pair of endplates to form an annular seal; and disposing the annular seal between a housing and a combustor liner with the finger elements sealing against the combustor liner.
 11. The method as in claim 10 wherein the outer diameter portion having at a terminus end of the gaps a keyhole formed therein.
 12. The method as in claim 10 wherein the finger elements having a foot portion at an outmost end for sealing engagement with a combustor liner.
 13. The method as in claim 10 wherein the annular seal is fixedly attached to the housing adjacent an exit nozzle.
 14. A method for air sealing between a housing and a combustor liner, the steps comprising: closing the gap between a housing and a combustor liner by inserting therebetween an annular seal comprising a plurality of diaphragm members laminated together between a pair of spacers and a pair of end plates; fastening the annular seal in a clamping mechanism on the housing adjacent a combustor exit nozzle; and sealing the gap between the housing and the combustor liner by seating a plurality of finger elements against the combustor liner interior wall to prevent air leakage into the combustor chamber. 